Method and device for the production of a longitudinal fold

ABSTRACT

A signature to be folded in a folding device is first provided with a pre-fold that is formed along the intended fold line. The signature is conveyed through a linear guide where it is pre-folded. The pre-folded signature is then delivered to a folding device where it is folded by being caused to pass between a pair of folding rollers.

FIELD OF THE INVENTION

The invention relates to a method and a device for producing alongitudinal fold in a signature by supplying the signatures to alongitudinal folding device with the signatures already provided with apre-fold.

DESCRIPTION OF THE PRIOR ART

Longitudinal folding devices and associated transport systems are knowngenerally from U.S. Pat. No. 4,746,108 as well as from German PatentPublication DE 32 39 799 C2.

A transport device for signatures in a folding device of a web-fedrotary printing press is known from U.S. Pat. No. 5,222,934, by means ofwhich the signatures are guided between two conveyor belts, are alignedat a stop and impact surface and are subsequently inserted into alongitudinal folding device for making a so-called third fold.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a method and a device forproducing a longitudinal fold, for example a so-called secondlongitudinal fold, at high production speeds.

Signatures to be provided with a longitudinal fold are clamped left andright of the intended fold line by, for example, upper and lowerconveyor belts and are then moved into position so that they can belongitudinally folded. Various pushing devices are usable to move thesignatures into the position where they are longitudinally folded. Thesignatures to be folded are provided with a pre-fold before they arelongitudinally folded.

The following advantages in particular are achieved by present theinvention. Time, as well as the alignment of the signatures while theyare stopped, is saved because of pre-forming the signatures along animaginary fold line while they are being conveyed to a folding device.Furthermore, the lift of the folding blade is drastically reduced bypre-forming the signatures. In accordance with further preferredembodiments, an up-and-down moving folding blade is completely omitted,so that the reversal of the direction of movement of the folding bladeis no longer needed and in this way the quiet running of the foldingdevice is improved. It is also possible in accordance with anotherpreferred embodiment of the invention to perform the complete foldingprocess in a straight conveying direction of the signatures.

BRIEF DESCRIPTION OF THE DRAWINGS

Several preferred embodiments of the present invention are representedin the drawings and will be described in more detail in what follows.Shown are in:

FIGS. 1 to 3, schematic representations of the method steps of themethod of the invention, in accordance with the present invention;

FIGS. 4 to 6, schematic representations of the method steps of themethod of the invention for a second preferred embodiment,

FIGS. 7 to 9, front views of devices in accordance with the inventionfor producing a fold,

FIG. 10, a top view of a further device for producing a fold,

FIG. 11, a lateral view F from FIG. 10,

FIG. 12, a lateral view of an embodiment of a device of the invention,but without an inlet panel and without signatures,

FIG. 13, a section along the line XIII--XIII of FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the method of the invention, a printed productcomposed of several sheets of paper, for example a signature 71 composedof several sheets, is grasped in a sandwich-like manner at its left andright elements or portions 72, 73 along, and parallel to an intendedfold line 74 by holding means, for example by upper and lower conveyorbelts 6, 7, 5, 10 as seen in FIG. 1, so that the elements or portions72, 73 are placed between the conveyor belts 6, 7, 5 and 10.Respectively one element 72 or 73 can also be grasped and guided byseveral conveyor belts 6, 7, 5, 10, not shown, which are arrangedparallel in relation to each other. The left and right elements 72, 73of the signature 71, originally spaced at a distance b1 are now movedtoward each other as far as a pre-selectable inner distance b2, measuredacross the top sheet of their ends 76, 77. Viewed in profile, the leftand right elements 72, 73 of the signature 71 perform a movement in theX-direction as well as the Y-direction of a right-angled coordinatesystem as depicted in FIG. 2. In the process, the belts 6, 7, 5, 10 alsochange their position in relation to each other, i.e. from their priorfirst position in the direction of the X-axis into an inclined position,wherein the edges of the belts 6, 7, 5, 10 are arranged in a V shapeseparated by the distance b2 of the ends 76, 77. Subsequently bothelements 72, 73 of the signature 71 are pressed together by a force P1,P2, as seen in FIG. 3 acting to the left and right of the fold line 74,so that a fold 78 is created. In this case the forces P1, P2 act in anarea close along the intended fold line 74 as shown in FIG. 3 and thedistance b between the ends 76, 77 is further reduced to b3 as depicted.The more the distance b of the lateral ends 76, 77 of the signature 71is reduced, the greater the movement of the left and right elements 72,73 of the signature 71 in the X-Y-direction. There is a distance f1between the ends 76, 77 of the signature 71 and a lowermost sheet 69 ofthe signature 71 at its fold line 74.

In accordance with a further preferred embodiment of the method of theinvention, based on the position of the signatures 71 in an X-direction(distance b1 of the ends 76, 77) or in a Y-plane as seen in FIG. 4, onlythe portions 79, 81 of the left and right elements 72, 73 of thesignatures 71 which are located in the area of the intended fold line 74are moved toward each other in the X- and Y-directions of a right-angledcoordinate system by the distance b4, shown in FIG. 5. In this case thelateral ends 76, 77, i.e. the long edges of the signature 71 only movein the X-direction of the right-angled coordinate system. In theprocess, the lowermost sheet 69 of a smoothed signature 71 is broughtalong its fold line 74 into a position on the Y-axis at a distance f2from the X-axis. A fold 78 shown in FIG. 6 is also created by thesubsequent action of forces P1, P2, which act on both sides of the foldline 74 on the portions 79, 81 or the close area next to the fold line74 of the signatures 71 and press them together. A representation indashed lines in FIG. 6 shows a fold in a signature 71 which was finishedlater.

During the movement, viewed in profile, of the left and right elements72, 73 of the signatures 71 in the X-, Y-direction, the signatures 71can be simultaneously moved in a transport direction C directed toward alongitudinal folding device 1, which is performed by means of theconveyor belts 6, 7, 5, 10 as seen in, for example FIG. 12. In this casea longitudinal guide 82 extending in the transport direction C andresiliently resting against the fold line 74 of the signatures 71 asshown in FIG. 5 can be provided above the fold line 74. This will bedescribed later. The left and right elements 72, 73 of the signature 71can be embodied to be symmetrical in respect to the fold line 74, i.e.be in the center, or asymmetrical.

To make the fold 78 in the signatures 71, the forces P1, P2 act in acompressing manner on the portions 79, 81 in the area of the fold line74 as seen in FIGS. 3 and 4. Different preferred embodiments of thedevice for producing a fold are shown in FIGS. 7 to 10. The transportdirection C simultaneously corresponds to an axis Z of a right-angledcoordinate system as seen in FIG. 11. A first longitudinal foldingdevice, identified as a whole by 80 as seen in FIG. 7, will be describedfirst. A folding blade 87, which cyclically moves up and down in thedirection toward and away from the folding gap 86 is disposed above twodriven folding rollers 2, 3 disposed axially parallel in respect to eachother, and whose rotational axes 83, 84 are evenly distanced from eachother, so that a folding gap 86 is created. In this case the signatures71 consisting of the left and right elements 72, 73 are alreadypreformed in the shape of a V because of the movement toward each otherof their left and right elements 72, 73, so that the folding blade 87need only have a short lift for producing a fold 78 in the signatures 71along the fold line 74 as seen in FIG. 7. The profile side of thefolding blade 87 oriented opposite the transport direction C of thesignatures 71 can be provided with a ground portion at least in itslower area, i.e. in the area of its edge, so that it can betterpenetrate the incoming signatures 71 with their raised left and rightelements 72, 73, if required.

In accordance with a further preferred embodiment of a secondlongitudinal folding device, identified as a whole by 88 as seen in FIG.8, a bar is disposed above the folding gap 86 between the axiallyparallel extending folding rollers 2, 3. In the axially paralleldirection in respect to the rotational axes 83, 84 of the foldingrollers 2, 3 this bar is provided with blower air nozzles 89, which blowair in the direction toward the folding gap 86. The signatures 71composed of left and right elements have already been pre-shaped in theform of a V, so that the force of the air directed on the fold line 74of the signatures 71 is sufficient to make a fold 78 in the signatures71 or to introduce the signatures into the folding gap 86 of the foldingrollers 2, 3 which are counter-rotating in the direction of theoutflowing blown air.

In a further preferred embodiment, a third longitudinal folding device,identified as a whole by 90 and as seen in FIG. 9, also has two drivenfolding rollers 2, 3 arranged axially parallel in relation to eachother, the same as the first and second longitudinal folding devices 80,88, and whose rotational axes 83, 84 are evenly spaced apart from eachother in such a way that a folding gap 86 is also created between thetwo folding rollers 2, 3. The folding rollers 2, 3 also rotatesynchronously in relation to each other and have carriers 93, 94respectively extending beyond their periphery 91, 92 in the axiallyparallel direction. The carriers 93, 94 can be embodied to be rigid andcan consist of a resilient material, for example of plastic. In anotherembodiment, the carriers 93, 94 can be movable, i.e. retractable intothe jacket of the folding rollers 2, 3, for example against the force ofsprings 96, 97 as seen in FIG. 9 or by means of controlled driveelements, not shown. In this case the carriers 93, 94 can be embodied inthe form of a bar or in the form of a plurality of bar segments arrangedone behind the other in the axially parallel direction 83, 84 on theperiphery 91, 92 of the folding cylinder 2, 3.

It is also possible to embody the folding rollers 2, 3 represented inFIG. 9 without the carriers 93, 94, and to provide folding rollerscounter-rotating in the direction of an inlet wedge in place of them,whose circular cross sections consist of respective semicircles withrespectively different radii, so that after each half turn of bothfolding rollers a common, but respectively different folding gap 86 iscreated. This folding gap 86 has the same effect as the carriers 93, 94.A common folding gap alternates with a slightly larger gap followingeach half turn of the folding rollers in relation to each other. Suchfolding rollers also rotate synchronously in respect to each other. Thevarious gaps are created mirror-reversed in respect to the fold line 74.

In a further preferred embodiment a fourth longitudinal folding deviceis identified as a whole by 99 as shown in FIG. 10. In this case anumber of folding rollers 101, 102, 103, 104, 106, 107, 108, 109 arearranged in the transport direction C of the signatures 71 to the leftand right of the fold line 74, and whose rotational axes 111, 112, 113,114, 116, 117, 118, 119 extend perpendicularly to the transportdirection C in the direction of the Y-axis of a right-angled coordinatesystem. The transport direction C corresponds to a Z-axis of athree-dimensional right-angled coordinate system. The clear distances d,e of a pair of rollers 111, 116, 104, 109 in the X-direction shown inFIG. 10 diminish in the transport direction C, so that by means of thisa folding gap with the distance "e" is also provided at the end, whichis equal to the folding gap 86. The folding rollers 101 to 104 and 106to 109 act compressingly on at least one portion 79, 81 of thesignatures 71 in the area of the fold line 74. A length "l" of thefolding rollers 101 to 104 and 106 to 109 can be of such dimensions thatthey only act in the area of the fold line 74, as shown in FIG. 11, orthese folding rollers can have a length corresponding to the width of aleft or right element 72, 73 of a signature 71. It is furthermorepossible, as represented in FIG. 5, to dispose a longitudinal guide 82above the signatures 71 in order to be able to better make the V-shapeddepression in the signatures 71, or to have, in addition to the holdingmeans 6, 7, 5 10 and possibly further guide means still to be described,means touching the bottom of the fold to be made. This longitudinalguide 82 can be embodied in different ways and can also cooperate with alower countersupport device 24 which may be seen in FIGS. 12 and 13.

In a generally known manner, a longitudinal folding device 1 as may beseen in FIG. 12, consists of a driven pair of folding rollers 2, 3, alongitudinal folding blade 4 moving cyclically up and down, severaldriven upper conveyor belts 6, 5 and driven lower conveyor belts 7, 10,which accept signatures 71, already provided with a first transversefold via driven belt guide systems 9, 11, from a folding apparatus 8 forlongitudinal folding and then pass them on to a device, not shown, forexample a paddle wheel. The upper conveyor belts 6, 5 as well as thelower conveyor belts 7, 10 extend further as far as downstream of thelongitudinal folding device 1 and are driven by belt rollers, not shown.However, for the sake of clarity the second belt rollers 12, 13 disposedin the vicinity of the folding apparatus 8 are embodied as driven beltrollers. The belt roller 12 is seated on both sides at the end of twoextension brackets 16, 17 fastened on a side frame 14 and extending inthe direction toward the folding apparatus 8. An inlet conduit 18, asshown in FIG. 13, is located centered between the lower conveyor belts7, 10 in the transport direction of the signatures 71 and extends,starting at the belt roller 13, horizontally in the direction of thelongitudinal folding device 1 and terminates directly into an inletwedge between the folding rollers 2, 3. The inlet conduit 18 is locatedbetween two inlet panels 121, 122, whose first long edges 123, 124 areinterlockingly connected with side frames or extension brackets 16, 17.Their second long edges 22, 23 are bent in the direction toward theconduit bottom or arched in the direction of the Y-axis (minus) at aradius corresponding to the radius of the folding rollers 2, 3. The longedges 22, 23 border the conduit bottom in the X-direction of theright-angled coordinate system or can cooperate with a counter-supportdevice, identified as a whole by 24. A line 74 of the futurelongitudinal fold extends in the center of the inlet conduit 18 and isdefined by a perpendicular line 28 in the Y-direction. Thecounter-support device 24 comprises a number of spherical pulleys 31,seated aligned behind each other in a rail 29, which support an upperrun 32 of an endless belt 33, whose lower run 37 is reversed via areversing roller 34 and which is driven via the belt roller 13, all asseen in FIGS. 12 and 13.

This rail 29 is pivotably seated by its first end 38 fixed on the sideframe on a shaft 39 which also supports the belt rollers 13. A secondend 41 of the rail 29 is frictionally and interlockingly connected withan adjusting device 42 fixed on the side frame, which allows thevertical adjustment of this second end 41 of the rail 29. A wheelarrangement 43 as an embodiment of the longitudinal guide 82 alsoextends in the alignment of the inlet conduit 18 above the belt systemor lower counter-support device 24 and parallel with it. This wheelarrangement 43 comprises a number of guide wheels 46 seated behind eachother aligned on a rail 44, each of which guide wheels 46 has a groove,semicircular in cross section, on its circumference for receiving thelower run 47 of an endless upper belt 48 of circular cross section. Theupper belt 48 extends in the production direction below the guide wheels46 parallel with the upper run 32 of the lower belt 33, its upper run 52is returned via a reversing roller 49 and a tension roller 51 and isdriven by the belt roller 12. With its first end 53 fixed on the sideframe, the rail 44 is pivotably seated on a shaft 54. A second end 56 ofthe rail 44 is frictionally and interlockingly connected with anadjustment device 57 fixed on the side frame, which allows the verticaladjustability of this second end 56 of the rail 44 against the force ofa spring, not shown. The guide wheels 46 of the upper rail 44 arerespectively disposed "staggered" in respect to the pulleys 31 of thelower rail 29, i.e. a straight line drawn through a rotational axis 59of a pulley and extending at right angles to the inlet conduit 18inclined in the direction toward the longitudinal folding device bisectsa distance "a" between two adjoining guide wheels 46 disposed on theupper rail 44, as shown in FIG. 12. The number of guide wheels 46 can beat a ratio of 1:1 or preferably a ratio of 2:1 in respect to the numberof pulleys 31. The even, i.e. quiet, passage of the signatures throughthe device of the invention during the pre-folding process is assured bymeans of this "staggered" disposition of the guide wheels 46 in respectto the pulleys 31.

The mode of operation of this longitudinal guide 82, which acts againstthe lower counter-support device 24, is as follows: The signatures 71conveyed from the folding apparatus 8 via the belt guide system 9, 11are conducted between the upper and lower conveyor belts 6, 7, 5, 10.Viewed in the production direction, the underside of the signatures 71rests centered on the upper run 32 of the belt 33. There is then adistance between the upper run 32 of the belt 33 and the lower run 47 ofthe belt 48, which corresponds to the thickness of the signatures 71.This distance can be preset by means of the adjusting devices 42, 57.During the conveyance of the signatures 71 by the conveyor belts 6, 7,5, 10, the belt 48 presses, in alignment with the future longitudinalfold 74, on the signatures 71 by means of the resilient force of therail 44. Because of the inclination of the lower rail 29 as well as theupper rail 44 by respectively 3° in relation to the horizontal, whilethe left and right elements 72, 73 of the signatures 71 remain in thehorizontal position, the signatures 71 are provided with a pre-fold of adepth of approximately 30 to 35 mm in the manner of an embossing or adeep-drawing process after their rear edge or rear border has left thebelts 33, 48. Their folds are finished in the longitudinal foldingdevice 1. In this respect the longitudinal folding process is two-stagedin that the signatures 71 are pre-folded on the fold line 74 and thefolding is subsequently finished in the longitudinal folding device 2,3, 4. The folded products are supplied to a paddle wheel, not shown,following the completion of this longitudinal fold 78. In the process,the folded products can be aligned front and back by means of two guidepanels before they reach the paddle wheel. The rear guide panel isidentified by 58 and shown in FIG. 12 of the drawings. The belt 33 canconsist of plastic of intermediate hardness with a textile insert. Thebelt 48 is embodied as a round belt and can also be made of plastic ofan intermediate hardness.

On their circumference the guide wheels 46 of the longitudinal guide 82can have a groove with a V-shaped cross section in place of a groovewith a semi-circular cross section for receiving the lower run 47 of thebelt 48, so that it is also possible to employ an endless belt with arhomboidal cross section.

In accordance with another embodiment of the longitudinal guide 82, theguide wheels 46 do not support a belt 48, but instead are driven bydrive elements, not shown, for example by means of toothed gearsdisposed on the same shaft with the guide wheels 46. In this case thewheel arrangement 43 can perform the function of a longitudinal guide 82wherein the left and right elements 72, 73 of the signature 71 are movedtoward each other at an inner distance "b", for example b4 as seen inFIG. 5, as well as act against a counter-support device 24 located belowthe wheel arrangement 43. In this case the distance f2 at its fold line74 of the lowermost sheet 69 in relation to its ends 76, 77 located inthe X-plane is at least twice the thickness of the signature 71.So-called "creasing" or permanent deformation of the paper fiber of thesignature 71 in the fold line 74 is caused respectively by thelongitudinal guide 82.

It is furthermore possible to embody the longitudinal guide 82 with aknife 82 with a dull edge in place of the guide wheels 46 as seen inFIG. 5.

The holding means embodied as upper and lower conveyor belts 6, 7, 5, 10can be guided in the surface of the inlet panels 121, 122, for examplein channels 126, 127 extending in the transport direction C and adaptedto the cross section of at least the lower conveyor belts 7. As alreadyexplained, several conveyor belts 6, 7, 5 10 can be disposed, extendingparallel to each other, in the inlet panels 121, 122.

The operation of the device for the production of a longitudinal fold inaccordance with the present invention can be summarized as follows:

A signature 71 consisting for example of several sheets is transported,"clamped" on its right and left element 73, 72 bordering the intendedfold line 74 between the upper and lower conveyor belts 6, 7; 5, 10. Inthe process the signature 71 undergoes a movement in the directiontowards the downstream located longitudinal folding device 1, 80 and inthe intended folding direction. The signatures 71 pass through apre-folding device 24, 82 on their way to the longitudinal foldingdevice 1, 80. The signature 71 is pre-folded in a "v-shape" in thispre-folding device 24, 82. The base line of the v-shaped pre-shape ofthe signature 71 forms the imagined fold line 74. On its way to thelongitudinal folding device 1, 80, the intended folding area isconsiderably lowered in the direction toward the intended foldingdirection. Such lowering is by 30 to 50 mm, for example. Lowered in thisway, the signature moves against a stop between the folding blade edgeof the folding blade 87 or in the pushing device, in the area of thegreatest approach of the folding rollers 2, 3, the folding roller gap86. The folding roller gap 86 can be adjusted within limits and can alsoby zero millimeters. In this case, the journals of the folding rollers2, 3 are resiliently seated. A distance between the lowermost positionof the signature 71 and the folding roller gap can be between 10 and 20mm. Subsequently the folding blade 87 merely needs to perform a movementoriginating in the interior of the inlet wedge area from an upperposition, i.e. a lifting movement of small lift length, for example 20to 30 mm, in a perpendicular direction in order to press the signature71 along the pre-formed fold line 74 between the rotating foldingrollers 2, 3. The rotational axes 83, 84 of the folding rollers 2, 3extend in this case next to, i.e. parallel with the intended fold line74.

The inlet wedge area between the two folding rollers 2, 3 has a contouras described below:

a connecting line extending in the horizontal direction at the place ofthe shortest distance between the folding rollers 2, 3; i.e. the foldingroller gap 86,

a quarter circle of the circumference of the left folding roller 2 asseen in FIG. 7 in the I. quadrant of a rectangular coordinate systemextending through the rotational axis 83 of the folding roller 2,

a quarter circle of the circumference of the right folding roller 3 asseen in FIG. 7 in the II. quadrant of a rectangular coordinate systemextending through the rotational axis 84 of the folding roller 3,

a horizontal connecting section between the highest points of thecircumferences at both folding rollers 2, 3.

In place of the up-and down-moving folding blade 87 it is of course alsopossible to provide a blower air device 89 or carrier bars 93, 94resiliently disposed in the folding rollers 2, 3. In this case thesignature 71, pre-formed in a v-shape, enters the longitudinal foldingdevice 1, 80 below the blower air nozzles 89. Because the weightyfolding blades 87 only need to perform a small lift, it is possible toconsiderably increase the folding speed.

The movement of the folding blade 87 originating from the interior ofthe inlet wedge area can also take place from an upper standby position.

I claim:
 1. A method for producing a fold in a signature including thesteps of:clamping a signature on the left and right of an intended foldline between upper and lower conveyor belts; feeding said clampedsignature along a signature transport path in a signature transportdirection; placing a signature pre-folding device in said signaturetransport path; passing said clamped signatures through said pre-foldingdevice; forming a prefold in said clamped signatures during passagethrough said pre-folding device; locating a signature longitudinalfolding device along said signature transport path after saidpre-folding device; providing first and second spaced rotary foldingrollers in said longitudinal folding device, said spaced folding rollersdefining an inlet wedge area and having a folding roller gap;positioning said spaced rotating folding rollers with rotational axesparallel with said folding roller gap; providing a pushing device actingperpendicularly with respect to said transport direction of saidsignatures for moving said signatures into said inlet wedge area and forpressing said signatures into said folding roller gap; supplying saidsignatures to said longitudinal folding device already prefolded by saidpre-folding device; moving said pre-folded signatures into said foldingroller gap by using said pushing device; and transporting saidpre-folded signatures through said folding roller gap by rotation ofsaid folding rollers to create a final fold in said pre-foldedsignatures.
 2. The method of claim 1 further including prefolding saidsignatures in a V-shape along an intended fold line in said pre-foldingdevice prior to entry of said signatures into said longitudinal foldingdevice from said pre-folding device.
 3. The method of claim 2 furtherincluding providing said pushing device as a folding blade having alower edge; and positioning said V-shaped prefolded signature portionsin said folding roller gap and originating movement of said foldingblade in said inlet wedge area for producing said fold in saidsignatures.
 4. A method for producing a fold in a signature includingthe steps of:clamping a signature left and right of an intended foldline between upper and lower conveyor belts; feeding said clampedsignatures along a signature transport path in a signature transportdirection; placing a signature pre-folding device in said signaturetransport path; passing said clamped signatures through said pre-foldingdevice; forming a pre-fold in said clamped signatures during passagethrough said pre-folding device; locating a signature longitudinalfolding device along said signature transport path after saidpre-folding device; providing two rotating folding rollers having afolding roller gap and an inlet wedge area in said longitudinal foldingdevice; positioning said two rotating folding rollers with theirrotational axes extending parallel with said folding roller gap;providing a signature pushing device having a lower folding edge whichis movable perpendicularly to said transport direction of saidsignatures to be folded into said folding roller gap; providing saidsignatures to be folded with a V-shaped deformation along their intendedfold line in said pre-folding device; moving said V-shaped deformationbetween said folding edge of said pushing device, which has dipped intosaid inlet wedge area, and said folding roller gap; inserting saidpre-folded signatures into said folding roller gap by downward movementof said pushing device; grasping said pre-folded signatures in an areaof an intended fold with said folding rollers; and transporting saidpre-folded signatures through said folding roller gap by rotation ofsaid folding rollers to create a final fold in said pre-foldedsignatures.
 5. The method of claim 1 further including terminatingmovement of said signatures in said transport direction prior tooperating said perpendicularly acting pushing device.
 6. The method ofclaim 4 further including terminating movement of said signatures insaid transport direction prior to operating said perpendicularly actingpushing device.
 7. The method of claim 1 further including moving saidsignature portions clamped on said left and right of said intended foldline in said pre-folding device toward each other a pre-selectabledistance.
 8. The method of claim 4 further including moving saidsignature portions clamped on said left and right of said intended foldline in said pre-folding device toward each other a pre-selectabledistance.
 9. The method of claim 7 further including moving saidsignature portions clamped on said left and right of said intended foldline toward each other while feeding said signatures in said pre-foldingdevice to said longitudinal folding device.
 10. The method of claim 8further including moving said signature portions clamped on said leftand right of said intended fold line toward each other while feedingsaid signatures in said pre-folding device to said longitudinal foldingdevice.
 11. The method of claim 1 further including arranging saidsignature portions clamped on said left and right of said intended foldline in said pre-folding device symmetrically with respect to saidintended fold line.
 12. A device for producing a fold in a signaturecomprising:spaced upper and lower conveyor belts extending along asignature transport path in a signature transport direction of asignature to be folded and adapted to clamp a signature on the left andright of an intended fold line; a signature pre-folding device locatedin said signature transport path; means feeding said signatures throughsaid pre-folding device along said signature transport path in saidsignatures transport direction to form a pre-fold in said signatures; alongitudinal signature folding device positioned after, along saidsignature transport path in said transport direction, said pre-foldingdevice, said folding device including driven folding rollers disposed tothe left and right of said fold line and rotatably supported axiallyparallel to said fold line and defining a folding gap; and a foldingblade moving cyclically up and down in said folding gap, said foldingblade forcing said pre-folded signatures into said folding gap.
 13. Thedevice in accordance with claim 12 wherein said folding blade isprovided with a folding blade edge which can be moved from a standbyposition in the direction of said folding roller gap and back to saidstandby position.
 14. A device for producing a fold in a signaturecomprising:spaced upper and lower conveyor belts extending along asignature transport path in a signature transport direction of asignature to be folded and adapted to clamp a signature on the left andright of an intended fold line; a signature pre-folding device locatedin said signature transport path; means feeding said signatures throughsaid pre-folding device along said signature transport path, in saidsignatures transport direction to form a pre-fold in said signatures; alongitudinal signature folding device positioned after, along saidsignature transport path in said transport direction, said pre-foldingdevice, said folding device including driven folding rollers disposed tothe left and right of said fold line and rotatably supported axiallyparallel to said fold line and defining a folding gap; and a barprovided with air nozzles directed into said folding gap and extendingaxially parallel with said folding rollers, said bar with air nozzlesforcing said pre-folded signatures into said folding gap.
 15. A devicefor producing a fold in a signature comprising:spaced upper and lowerconveyor belts extending in a transport direction of a signature to befolded and adapted to clamp a signature on the left and right of anintended fold line; means feeding said signatures along a pre-foldingdevice in said signatures transport direction to form a pre-fold in saidsignatures; and a longitudinal signature folding device positionedafter, in said transport direction, said pre-folding device, saidfolding device including driven folding rollers disposed to the left andright of said fold line and rotatably supported axially parallel to saidfold line and defining a folding gap, said folding rollers each havingcarriers positioned axially along their peripheral surfaces andextending beyond said peripheral surfaces.
 16. The device of claim 12wherein said pre-folding device includes a plurality of pairs ofpre-folding rollers positioned to the left and right of said fold lineand having rotational axes which extend perpendicularly to saidtransport direction, each roller in each of said pairs of pre-foldingrollers being equally spaced from said fold line, said pre-foldingrollers acting on said signatures at least in the immediate area of saidfold line.
 17. The device of claim 15 wherein said carriers are arrangedon a bar in a jacket surface of said folding rollers.
 18. The device ofclaim 17 wherein said carriers extend in said jacket surface of saidfolding rollers on sections of said bar disposed axially behind eachother.
 19. The device of claim 15 wherein said carriers are rigid. 20.The device of claim 15 wherein said carriers are resilient.
 21. A devicefor forming a pre-fold along an intended fold line in a signature to befolded in a signature folding device comprising:first and second spacedinlet panels positioned in a transport direction of signatures to befolded before said signatures folding device, said spaced inlet panelsdefining an inlet conduit; first long edges of said inlet panelsconnected with a frame of said signature folding device; second longedges of said inlet panels being bent in a direction toward a conduitbottom of said inlet conduit; a longitudinal guide extending in saidtransport direction and disposed above said conduit bottom of said inletconduit, said longitudinal guide being adjustable to vary an inclinationof said longitudinal guide; and signature holding, means extending alongsaid inlet panels and movable in said transport direction.
 22. Thedevice of claim 21 wherein said longitudinal guide is a knife.
 23. Thedevice of claim 21 wherein said longitudinal guide is a roller supportincluding a rail and having a plurality of guide wheels seated alignedalong said rail in said transport direction.
 24. The device of claim 21wherein a first end of said rail is pivotably supported by a shaft whichalso receives a belt roller and further wherein a second end of saidrail is adjustable against a lower counter-support device by anadjustment device secured to said frame.
 25. The device of claim 23wherein said guide wheels are driven.
 26. The device of claim 23 whereineach of said guide wheels has a circumferential groove which issemicircular in cross-section.
 27. The device of claim 24 wherein saidguide wheels, on their sides facing said counter-support device guide alower run of an endless belt.
 28. The device of claim 27 wherein each ofsaid guide wheels has a circumferential groove with a V-shapedcross-section and further wherein said endless belt has a rhomboidshaped cross-section.
 29. The device of claim 24 wherein saidcounter-support device includes a plurality of spaced pulleys secured toa counter-support rail, said pulleys supporting an upper run of anendless driven belt.
 30. The device of claim 29 wherein a first end ofsaid counter-support rail is pivotably seated on a shaft which alsosupports a belt roller and further wherein a second end of saidcounter-support rail is adjustable with respect to said longitudinalguide by a counter-support adjustment device secured to said side frame.31. The device of claim 29 wherein a straight line drawn through arotational axis of one of said counter-support pulleys and which extendsat a right angle to said inlet conduit bisects a spacing distancebetween adjacent ones of said guide wheels on said rail of said rollersupport.
 32. The device in accordance with claim 31 wherein a ratio ofthe number of guide wheels to the number of pulleys is 1:1.
 33. Thedevice in accordance with claim 31 wherein a ratio of the number ofguide wheels to the number of pulleys is 2:1.
 34. The device of claim 21wherein said signature holding means consists of upper and lowerconveyor belts which grip left and right elements of a signature to befolded in a sandwich-like grip.